How to Install macOS 10.12 Sierra on an External Drive (Hard Drive, Solid State Drive or Flash Drive)

Mac OS X is one of the world’s leading, most well known operating systems. For years it has been at the center of every Mac computer. Now in 2016, Apple has announced the latest version of masOS, 10.12 Sierra. With it comes lots of new features and changes. However you may not want to install right away on your mac without trying it out first. The best way to try out the latest version of macOS is by installing it on a separate external drive first.

By installing it on an external drive, you will get the chance to test it and make sure everything works properly without updating your existing operating system. It’s pretty easy to do and all you need is a Mac and an external drive to install it on.

Requirements and Notes:

You will need a Mac computer which is compatible with macOS 10.12 Sierra

You will need an external hard drive, solid state drive or flash drive of at least 20GB capacity

Download the macOS 10.12 Sierra installer from the link above and extract it from the .zip or .dmg file.

Plug your external drive into you Mac and open Disk Utility. Click on the drive in the left hand menu. Click the ‘Erase’ button at the top. Make sure the format is set to ‘Mac OS Extended (Journaled)’ and the scheme is set to ‘GUID Partition Map’ . Click ‘Erase’ and wait for it to complete. Now close Disk Utility

Now open the macOS Sierra installer file. Run through the installer until you are asked which drive to install to. Make sure you select the drive you erased in Disk Utility. Choosing the wrong drive could update your main OS.

Click ‘Install’ and the install process will begin. Once the install has finished, your Mac will boot from the external drive for the first time. You can now set it up as you would a new Mac.

You now have macOS Sierra installed on an external drive! To boot from that drive in future, hold down the ‘Alt’ or ‘Option’ key on the keyboard while booting. You will be asked which drive you want to boot from. Select the external drive.